Concrete batch fabrication plants are well known and typically comprise a source of plant water, and storage facilities for storing fresh cement powder, sand, and gravels or other aggregates of various sizes to be admixed with the cement powder and water when a batch of concrete is made. Such plants, typically called "ready-mix" plants, are under the control of an operator, and may have a computerized batching console for selecting the proportions of the various constituents to be admixed. In this latter type of installation, the batching console is monitored by the plant operator. Fresh batched concrete mix is dispensed into one or more waiting trucks each having a revolving drum which is used to transport the fresh batched concrete mix to one or more job sites for pouring. After a concrete pour has been made, each truck typically returns to the concrete fabrication plant where a fresh batch of concrete is poured into the truck mixing drum for transport to the job site. This cycle continues throughout the production day, or until no more fresh concrete mix is required at any of the job sites. At the end of a production day, each truck is washed out to remove the accumulated deposits within the mixing drum, and parked until the next production day.
For years, the concrete remaining in a returning truck was simply dumped in the yard and permitted to harden, and was later hauled away for use as land fill. This arrangement was wasteful in that reusable constituents of the returned concrete were being thrown away. In addition, the dumping of returned concrete in a yard was environmentally unsound.
Accordingly, various types of apparatus have been designed for reclaiming some or all of the components of the returned concrete mixture, to provide a less environmentally damaging operation.
In a relatively recent development, U.S. Pat. No. 4,226,542 issued to Black et al, teaches a partial separation of the slurry of cement and water, wherein water from the slurry is clarified and reused as water within the ready-mix plant. The heavier cement and sand slurry solids are allowed to settle out of the slurry. Both the slurry solids and the clarified water are re-used, so landfilling is avoided. But the Black et al system is relatively complex and costly, as both the slurry solids and the clarified water must be monitored and controlled.
There remains a need for reclamation apparatus and methods, for reclaiming fluid concrete mix, which are economical to obtain and use. Such apparatus and methods should use a minimum amount of water and other resources, should be simple to use and maintain, and should fit economically into the routine operation of the concrete plant.